Knee Prosthesis Research Articles (Page 1)

This paper reviews the latest methods for creating control interfaces for intention detection in active transfemoral prosthetic devices. A literature review over the past two decades identified several control algorithms for intention detection. Sources included scientific publications, books, and online resources focusing on knee prostheses. Three main areas of research were identified. The studies were assessed using the Downs and Black checklist, detailing their control techniques and performance assessments. Initially, 213 studies were retrieved; 33 were selected for this review. Fifteen (15) papers examined control strategy frameworks and goal outputs of active prosthetic legs. Two (2) papers discussed conventional control methods for transfemoral prosthetic legs. Four (4) studies explored potential implementations of intention detection, and twelve (12) papers investigated machine learning algorithms for active prosthetic legs. The review suggests using a simpler sensory system paired with innovative control algorithms to translate limited sensor data into a broader set of relevant information. Effective sensory systems and intention detection algorithms are crucial for active transfemoral prosthetic limbs. This review presents the feasibility of control interfaces that enable intention detection for active prosthetic legs, offering multiple references and classifying different works in the field.

Intraoperative femoral condylar avulsion fractures during total knee arthroplasty (TKA) are rare but potentially lead to joint instability and poor outcomes if not properly managed. However, the necessity of using condylar-constrained prostheses in these cases remains controversial. This retrospective study examines the incidence, management approaches, and radiological outcomes of these fractures. A total of 47 patients (11 males, 36 females; mean age 67.1 ± 7.0 years) with femoral condylar avulsion fractures were identified from 4290 TKAs performed between January 2008 and December 2022, matched with nonfracture patients at a 1:1 ratio by age, gender, and BMI. Intraoperative fractures were treated using cancellous bone screws or nonabsorbable sutures based on the size of the fracture fragment, without the insertion of condylar constrained prostheses. All patients underwent outpatient follow-up, with data collected on preoperative diagnosis, body mass index (BMI), knee range of motion (ROM), and type of prosthesis used. Key radiological indicators assessed included proximal tibia varus angle (PTVA), distal femoral valgus angle (DFVA), joint line congruence angle (JLCA), hip-knee-ankle angle (HKA), and preoperative subluxation status. The incidence of femoral condylar avulsion fracture in primary TKA was found to be 1.1%. Over a follow-up period of 1.5-3 years, no instability was noted in any patients. Significant differences were observed between fracture and nonfracture groups in PTVA (82.02 ± 3.39 vs. 85.32 ± 1.87, p = 0.01), DFVA (85.53 ± 2.73 vs. 87.51 ± 5.29, p = 0.02), and HKA (8.81 ± 3.30 vs. 6.53 ± 2.21, p = 0.01). However, the Knee Society Score (KSS) at last follow-up showed no statistical difference (p = 0.05). Femoral condylar avulsion fractures during primary TKA may be linked to joint deformities. Fixation methods using cancellous bone screws or nonabsorbable sutures, combined with a hinged knee brace, resulted in favorable clinical and radiological outcomes, with no need for prosthesis modification.

Background/Objectives: The rate of periprosthetic joint infection (PJI) is expected to increase in the next years worldwide, mainly due to increasing volume of total joint replacement, longer prosthesis lifespans, and patients with multiple comorbidities. The aim of this study is to describe our personal technique, the modified Hofmann Articulated Spacer (mHAS), in which a CR femoral shield and a partially threaded cannulated screw are inserted into the liner replicating a tibial stem, and to evaluate the efficacy of the spacer as a definitive treatment option in selected patients with knee infections. Methods: A consecutive series of 132 patients were treated for orthopedic infection at the Orthopedic and Trauma Center, University of Turin, between November 2023 and May 2025. All patients included in the study had undergone knee prosthesis removal followed by the implantation of a modified Hofmann Articulated Spacer (mHAS). Functional recovery was evaluated through clinical examination, particularly knee range of motion, and patient-reported outcome measures (PROMs), including the Knee Society Score (KSS), Oxford Knee Score (OKS), and the EQ-5D-5L Visual Analogue Scale (VAS). Results: Nine patients were enrolled in the study, at a mean follow-up of 8.12 months (range: 3–13). The mean range of motion of the knee was 95 degrees (range: 80–120°, SD: 15°). The Knee Society Score (KSS) presented a mean value of 71.9 (SD: 18.11). The Oxford Knee Score (OKS) showed a mean value of 30.8 (SD: 8.5). The EuroQol-5 Dimension-5 Level Visual Analogue Scale (EQ-5D-5L VAS) scores demonstrated an excellent quality of life among the participants. Conclusions: The Modified Hofmann Articulated Spacer demonstrated good functional, qualitative outcomes and eradication rates in patients who underwent the first-stage revision TKA for PKI. This has led us to propose it as a definitive treatment option for more critical and low-demand patients and to postpone the second-stage surgery in the remaining cohort due to satisfactory spacer joint function without pain.

Predicting Outcomes of Periprosthetic Joint Infection Treated with Debridement, Antibiotics, and Implant Retention (DAIR): An External Validation of the KLIC (Kidney, Liver, Index Surgery, Cemented Prosthesis, C-reactive Protein) Score.

Abstract With the increasing number of primary knee prosthesis implantations and the demographic changes, the number of periprosthetic fractures is also rising. Their treatment often proves to be challenging.Standard diagnostics consist of conventional X-rays with a calibration object. For prosthesis planning, the adjacent joints should also be image, x-rays of the contralateral side can be helpful. The imaging is usually supplemented by a CT scan to better assess the prosthesis fit and bone quality. Based on the imaging, the fracture can be classified according to Rorabeck or UCS, although the prosthesis fit cannot always be definitively determined. The prosthesis model and implantation date should be identified, ideally through the implant pass and surgical report.In surgical treatment, osteosynthesis aiming to preserve the prosthesis should be attempted, if technically feasible. Indications for a prosthesis exchange include loose prosthesis, a well-fixed prosthesis with poor or reduced bone quality that does not provide sufficient fixation for osteosynthesis, fractures with a high risk of pseudarthrosis, ligamentally unstable prosthesis, or periprosthetic fractures in geriatric patients, when an osteosynthesis doesn’t allow primary full weight bearing. However, due to limited data, no general recommendation or algorithm can be provided; decisions must be made on a case-by-case basis.Until definitive treatment, temporary immobilization with an external fixator may be necessary. Technically, a prosthesis exchange is a complex operation consisting of four main steps: patient in dorsal decubitus and medial arthrotomy, resection of the distal femur and preparation of the femoral canal, removal of the tibial component and tibial preparation, followed by determination of the prosthetic components and implantation.The particular challenge lies in correctly restoring the joint line and especially the femoral rotation.The complication rates and outcomes do not differ significantly from osteosynthesis according to several current reviews and meta-analyses.

Complications of distal femur megaprostheses.

Rivaroxaban, an oral direct anticoagulant that is a selective inhibitor of Xa factor, was commercialized in Belgium in 2009 with as unique reimbursed indication the prevention of thromboembolic events before a programmed hip or knee prosthesis. Since that time, both the efficacy and safety of rivaroxaban have been validated in a variety of indications : prevention and treatment of venous thromboembolic disease with or without pulmonary embolism, non valvular atrial fibrillation, symptomatic coronary disease and peripheral arteriopathy. Different presentations are currently available from 2.5 mg to 20 mg to allow the practitioner adjust the dosage of rivaroxaban to the specific indication (for instance, in patents with symptomatic atheromatous cardiovascular disease, 2 x 2.5 mg/day in combination with a antiplatelet agent).

A nine-year retrospective study of bacterial epidemiology and culture optimization in four orthopaedic surgery departments.

Semi-constrained and constrained knee arthroplasty for distal femur nonunion & mal-union.

Compatibility of Retrograde Intramedullary Nails with Knee Prostheses: A Comprehensive Analysis.

Reliability of a modified Berger protocol for TKA component rotation using an anatomical tibial component.

Satisfaction after total knee arthroplasty (TKA) is considered akey success parameter but is subject to avariety of individual and methodological influencing factors. Historically, adissatisfaction rate of around 20% has been reported, which should be considered in adifferentiated manner and adapted to the current data situation. Satisfaction is not to be equated with the absence of dissatisfaction; neutral assessments should be taken into account. PROMs are also subject to various limitations as measurement instruments. In addition, there are valid risk factors for postoperative dissatisfaction after knee prosthesis implantation. Both the clinical assessment of experienced surgeons and AI-based prediction models show potential for predicting postoperative satisfaction.

Over ten year follow-up results of a prospective and consecutive series of primary total knee arthroplasty with a multimodular total knee prosthesis.

BackgroundA lack of evidence of compelling clinical benefits is a key factor limiting the adoption of commercialized powered robotic knee prostheses into mainstream clinical practice. Previous studies have demonstrated mixed results, potentially due to a combination of limitations in prosthetic hardware, control algorithms, and testing methodologies.MethodsWe investigated the clinical effects of a commercialized robotic knee prosthesis (the latest generation Össur Power KneeTM) with n=7 above-knee amputee participants. Participants with both higher (K4) and lower mobility (K3) completed a series of experiments including repeated sitting and standing, a stand, walk, sit shuttle test, and fast walking on a treadmill. We tested both standard (ÖSSR) and novel (HKIC) control policies and compared the resulting clinical metrics to those found with the users’ prescribed passive prostheses. Our experiments were physically demanding, which could help elucidate the potential benefits of powered knees.ResultsThe clinical effects of the Power Knee varied with mobility level and the control policy used. The phase-based controller often produced stronger walking and sit/stand improvements for the higher mobility group compared to the default controller, though it also presented a steeper learning curve and reduced walk-to-sit transition speed. Conversely, the default control policy was perceived as easier to master but was less assistive to the higher mobility group and produced slower sit/stand cycles. Lower mobility participants experienced improvements in standing speed (HKIC: 36.7pm 15.1% faster, p<0.001; ÖSSR: 28.8pm 15.1% faster, p=0.001), inter-limb ground reaction force symmetry (HKIC: -0.214pm 0.068, p<0.001; ÖSSR: -0.199pm 0.068, p<0.001), and inter-limb peak knee moment symmetry (HKIC: -0.290pm 0.126, p<0.001; ÖSSR: -0.284pm 0.126, p<0.001) during sit-to-stand tasks relative to their passive prostheses. In contrast, higher mobility participants benefited less in sit/stand but showed improvements while walking including increased toe clearance (HKIC: 25.4pm 12.2 mm, p<0.001; ÖSSR: 13.4pm 12.2 mm, p=0.033), greater early stance knee flexion (HKIC: 7.1pm 2.9^circ , p<0.001; ÖSSR: 4.5pm 2.9^circ , p=0.005), and, for the HKIC policy, a reduced swing-phase peak hip flexion moment (HKIC: -0.18pm 0.11 Nm/kg/(m/s), p=0.003). Despite these biomechanical improvements and qualitative reports of reduced effort, neither control policy produced significant benefits in endurance or repeated task performance compared to the passive condition. Sit-to-stand cycle count in the lower mobility group was unchanged (HKIC: p=0.268, ÖSSR: p=0.848), and it was reduced in the higher mobility group with the ÖSSR condition (2.0pm 1.4 fewer, p=0.007). In the shuttle walk test, laps completed by higher mobility users decreased with HKIC (157.3pm 46.3 fewer, p<0.001), and no significant differences were found for lower mobility users. No significant changes in fast walking distance or speed were observed across conditions.ConclusionsThe latest generation Power Knee can create clinical improvements in walking and sit/stand behaviors compared to passive (microprocessor) knees, though the effects are sensitive to the user’s mobility level and the Power Knee’s control policy. However, these improvements did not directly translate to improved functional performance or endurance. Some negative effects of the Power Knee were also observed including reduced agility, slower transitions, and thermal limitations, though some of these limitations could potentially be addressed through future control innovations or with more thorough acclimation. The observed benefits motivate future longitudinal studies to investigate the clinical effects of robotic knees compared to passive (microprocessor) knees in real-world settings and to elucidate how they could be best utilized in clinical practice.Trial Registration: The experimental protocol was approved by the University of Michigan Institutional Review Board (HUM00230065) on February 9th, 2024. The trial is registered with the National Institutes of Health under ClinicalTrials.gov ID NCT06138977.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12984-025-01729-2.

Introduction. The composite materials (4P+2C) and (4P+4C) that are used in manufacturing the below knee prostheses socket were subjected to mechanical tests tensile and bending constant and variable loading at stress ratio R = -1 and room temperature (RT25-30°C ). During the gait cycles, fatigue tensile and compression stress are induced. Methodology. The thickness and weight of the fatigue samples were 2 and 2.7 mm, 2.954 and 3.42 (gm) respectively. The increase in thickness and weight showed an increase in (UTS)tensile (UTS) bending, ET modulus of elasticity in tensile and Eb modulus of elasticity in bending by 18.84% 7.72%, 36.36% and 15.06% respectively. Results: While this increase improved the fatigue strength at 106 cycle and fatigue life at 60 MPa applied stress by 82.9% and 78.88% respectively. Increasing and decreasing fatigue variable program was carried out for the two composites. Discussion. Applying Miner rule to the obtained experimental results showed that Miner theory is not capable to predict safe fatigue life and its overestimated the fatigue properties. Conclusions. Proposed non-linear fatigue model was suggested and it applied to the experimental data. The fatigue results obtained from this model have a good agreement with those obtained experimentally

Background. Aseptic loosening of the knee prosthesis components is one of the most common causes of revision surgery. The acceptable range of angular values for postoperative alignment of the lower limb and the frontal positioning of the prosthetic components remains a subject of debate. The aim of the study — to identify the predictors of the early aseptic loosening of prosthetic components following primary total knee arthroplasty. Methods. The study group included 31 patients with aseptic loosening of prosthetic components. The comparison group consisted of 55 patients with no signs of loosening over a follow-up period of at least 8 years. Baseline characteristics (sex, age, body mass index, and operated side) were compared, along with preoperative and postoperative angular alignment of the lower limbs, specifically, the anatomical femorotibial angle (aFTA) and the hip-knee-ankle angle (HKA), as well as reference angles for prosthetic component positioning. Results. Patient age over 60.5 years and BMI over 27.5 were associated with a 2.9-fold and 2.6-fold increased risk of prosthetic loosening, respectively. Preoperative varus deformity, with an HKA angle exceeding 9.5° and an aFTA over 6.5°, increased the risk of loosening by 9.6 and 23.1 times, respectively. Postoperative residual deformity exceeding 0.5° in either direction, as measured by the aFTA, increased the risk of loosening by 8.7 times. Valgus positioning of the tibial component was associated with a 2.8-fold increased risk of component loosening. Conclusions. In elderly and overweight patients with pronounced varus deformity of the lower limb, personalized preoperative planning should be prioritized to prevent early aseptic loosening of prosthetic components. In cases where postoperative residual deformity or valgus positioning of the tibial component is detected, enhanced clinical follow-up with radiographic monitoring every 6 months is recommended. If radiolucent lines progress and pain is present, early consideration of revision surgery is advisable, as it may increase the likelihood of a successful conservative revision.

Objectives: Materials with ceramic surface treatments have been adopted in total knee arthroplasty (TKA) to limit polyethylene wear and thus extend implant longevity. This study evaluated, at a single center, mid-term survivorship and clinical outcomes for a mobile-bearing knee prosthesis with a titanium–niobium nitride (TiNbN) coating. Methods: A total of 150 patients who underwent primary cemented TKA using the same TiNbN-coated mobile-bearing prosthesis were identified through the institutional database. Of these, 102 patients (102 knees) attended the follow-up examination and provided informed consent to participate in this study. All patients underwent comprehensive clinical and radiological assessment. Primary outcomes were the Forgotten Joint Score (FJS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS). Results: After a mean follow-up period of 7.9 years, two revision surgeries were recorded. One revision was performed due to late periprosthetic joint infection, while the other involved synovectomy and liner exchange due to persistent stiffness and pain. At 9 years follow-up, overall survivorship of the TiNbN-coated TKA was 97.1% (95% CI, 88.4–99.3%). Mean FJS and KOOS were 70.0 (range 29–100) and 70.6 (range 24–98), respectively. No sex-based differences were detected in clinical outcomes or implant survivorship. Conclusions: The TiNbN-coated mobile-bearing knee prosthesis demonstrated favorable mid-term survivorship and patient-reported outcomes. These findings support its use as a treatment option for knee osteoarthritis, with performance comparable to contemporary TKA designs.

Mid-to-long-term outcomes of posterior-stabilized type total knee arthroplasty in asian patients: A single-center retrospective cohort study.

Although metal blocks have been widely used for reconstructing uncontained tibial bone defects, the influence of their elastic modulus on the stability of tibial prosthesis fixation remains unclear. Based on this, a finite element model incorporating constrained condylar knee (CCK) prosthesis, tibia, and metal block was established. Considering the influence of the post-restraint structure of the prosthesis, the effects of variations in the elastic modulus of the block on the von Mises stress distribution in the tibia and the block, as well as on the micromotion at the bone-prosthesis fixation interface, were investigated. Results demonstrated that collision between the insert post and femoral prosthesis during tibial internal rotation increased tibial von Mises stress, significantly influencing the prediction of block elastic modulus variation. A decrease in the elastic modulus of the metal block resulted in increased von Mises stress in the proximal tibia, significantly reduced von Mises stress in the distal tibia, decreased von Mises stress of the block, and increased micromotion at the bone-prosthesis fixation interface. When the elastic modulus of the metal block fell below that of bone cement, inadequate block support substantially increased the risk of stress shielding in the distal tibia and fixation interface loosening. Therefore, this study recommends that biomechanical investigations of CCK prostheses must consider the post-constraint effect, and the elastic modulus of metal blocks for bone reconstruction should not be lower than 3 600 MPa.

CT-based radiostereometric analysis (CT-RSA) is an alternative to RSA to measure implant migration. We performed a clinical validation study using VoluMetric Matching Micromotion Analysis (V3MA) software for CT-RSA. The aims of this study were to assess the agreement between V3MA and Model-based RSA software (for RSA), and to determine the interobserver agreement in V3MA. On a subset of patients included in a clinical trial, knee prosthesis tibial implant migration was measured between 1 and 5 years postoperative with V3MA and Model-based RSA software. V3MA and Model-based RSA results were compared by assessing the mean differences and limits of agreement (mean ± 1.96* standard deviation) using Bland-Altman analysis. V3MA migration results of two observers were compared using intraclass correlation (ICC) and Bland-Altman analysis. Twenty-four patients were included in the analysis. The mean difference (limits of agreement [LOA]) was -0.14 mm [-0.88 to 0.60] for maximum total point motion (MTPM). LOA for translations and rotations did not exceed ±0.5 mm and ±1°, respectively. The ICC (95% confidence interval) for MTPM between observers was 0.995 (0.989-0.998), and the mean difference [LOA] was 0.04 mm [-0.17 to 0.24]. We showed that between 1 and 5 years postoperative, V3MA migration results were comparable to those of Model-based RSA for cemented tibial component migration in a clinical study. The interobserver variability showed excellent agreement for V3MA. Overall, V3MA is a valid alternative to Model-based RSA for the analysis of tibial component migration in TKA with medium-term follow-up.